Biel, 36, and Timberlake, 37, were smiling throughout the sporting event, even posing for pics for fans inside the croquet club.

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And at one point, they couldn't seem to contain their laughter, as documented in this sweet picture:

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Serena Williams won big on Tuesday, in a comeback victory against Italian tennis pro Camila Giorgi, 3-6, 6-3, 6-4. Throughout the match, Timberlake could be seen getting up from his seat to applaud the 36-year-old tennis pro.

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Williams will now advance to the women's semi-finals, where she'll compete against Julia Goerges from Germany. She's now only one match away from challenging Margaret Court's record 24 Grand Slams.

"I feel good, I feel like I did better today, I had to," Williams, who welcomed her first child, daughter Alexis Olympia, last September, told BBC Sport following the match. "This is only my fourth tournament back [since giving birth] so I don't feel pressure, I don't feel I have to win this. I still have a long way to go to be where I was."

Williams has had plenty of celebrities flock to London to cheer her on during the historic tennis tournament, including Pippa Middleton, Michelle Dockery, Stella McCartney, Alexa Chung, Drake and Billie Jean King. The tennis star's husband, Alexis Ohanian, has also been supporting her, adorably serving us with a handful of epic facial expressions.